In some applications, for example in the context of motor vehicle technology (the engine control), it is of significance to know which temperature is present in a mass flow line provided with a throttle valve. In such an engine control, such temperature values are evaluated in the determination of actuating quantities of the engine in dependence upon an input value (see, for example, DE-A 196 18 385). A further application of the evaluation of such a temperature value is defined by the formation of actual quantities in the context of the engine control, for example, in the context of load detection (see, for example, U.S. Pat. No. 6,588,261). The temperature of the in-flowing gas ahead of the throttle position is of interest especially for considering the instantaneous density of the gas.
The determination of this temperature can take place via a corresponding temperature sensor which, however, is not recommended because of complexity and cost. Furthermore, an estimate of this temperature can be made on the basis of the temperature downstream of the throttle flap in the mass flow line by setting the temperatures forward and rearward of the throttle position equal. The temperature downstream of the throttle position is measured. This approximate determination of the temperature ahead of the throttle position is then no longer accurate enough when a mass flow is supplied between the throttle position and the temperature measurement downstream of the throttle position with this mass flow having a temperature which is significantly different from the temperature forward of the throttle position. Then, a mixture temperature of these two temperature quantities is measured downstream of the throttle position. In internal combustion engines, exhaust gas is introduced into the intake manifold between the throttle flap and the intake manifold temperature sensor (exhaust-gas recirculation). This exhaust gas has a relatively high temperature so that the mixture temperature, which is measured in the intake manifold, differs significantly from the temperature ahead of the throttle flap. The error, which is caused by setting the two temperatures equal in this case, is not satisfactory in view of the accuracy of the engine control.
The same applies when the temperature ahead of the throttle position is to be measured and the temperature downstream of the throttle position is to be estimated or when an estimate of the temperature of the additionally introduced gas is to be determined without measurement.